[U-Boot] ORIGEN: fix needed for out-of-tree build

Dear Chander, when building the "origen" board out-of-tree, it poollutes the source directory with a file board/samsung/origen/tools/mkorigenspl.exe which then never gets cleaned up.

Please fix your Makefile for out-of-tree building.

Side-note: Why is this file called ".exe"? Is this some MSDOS executable or what? Please consider also fixing the name.

Thanks.

Best regards,

Wolfgang Denk